1. Field of the Invention
This invention relates to a method of manufacturing an insulating film, a method of manufacturing a transistor, and a method of manufacturing an electronic device, and more particularly relates to a method of manufacturing a spin-on-glass insulating film, a method of manufacturing a transistor in which a spin-on-glass insulating film is used as a gate insulating film, and a method of manufacturing an electronic device in which a spin-on-glass insulating film is buried within a trench.
2. Description of the Related Art
As a method of forming a silicon (Si) oxide film on a substrate such as a silicon substrate and a glass substrate, a physical vapor deposition (PVD) method, a chemical vapor deposition (CVD) method, a spin-on-glass method, or the like are known. In particular, with the spin-on-glass method which provides high versatility, silicon (Si) oxide films can be formed with lower costs, as described in Japanese Patent Laid-Open Publications Nos. 2001-319927, 2002-367980, and 2004-241751.
A polysilazane coated film which includes Si—N (nitrogen) bonding group, Si—H (hydrogen) bonding group, and N—H bonding group in the basic skeleton is used for the spin-on-glass method. The polysilazane coated film is a liquid material and is generally coated by spin coating. The polysilazane coated film which is spin-coated is subject to a heat treatment in a water-vapor (H2O) atmosphere or an oxygen (O2) atmosphere to convert the Si—N bonding group or the Si—H bonding group into the Si—O bonding group, so that a silicon (Si) oxide film can be formed.
While the above-described spin-on-glass method is advantageous in that the method provides high versatility and allows formation of an Si oxide film with low costs, the method has a problem that there the Si—N bonding group or the Si—H bonding group remain in the Si oxide film which is formed. Consequently, the Si oxide film which is formed by the spin-on-glass method has lower electrical characteristic, particularly lower withstand voltage and higher leakage current compared to that of a boron phosphorous silicate glass (BPSG) film or a tetra ethyl ortho-silicate (TEOS) film.
When a silicon (Si) oxide film formed by the spin-on-glass method is used as a gate insulating film of a thin film transistor (TFT) of a liquid crystal display device, for example, defects resulting from short circuit are generated due to poor dielectric strength between the gate electrode and the channel forming region (or the source region or the drain region). Further, as the leakage current increases in the thin film transistor, power consumption of the liquid crystal display device is increased.